Once we have this fancy new code, it will provide a stable and robust base for building new features. The DVCS systems have done a great job exploring new areas and needs of version control users. One feature in particular is called stashing or shelving (see "git stash" and "hg shelve").
For those not familiar with the stash concept: consider the scenario where you've been doing some work, and a high-priority bug arrives, needing to be fixed right away. Classically, a Subversion user would check out a fresh working copy, fix the bug, perform the commit, and go back to their work in the original working copy. Instead, when using stash, it takes all of your current work and sets it aside, leaving you with an unchanged working copy, ready for your bug-fix work. After your commit, you retrieve the changes that were stashed. The presumption here, of course, is that stashing is a much faster and simpler operation than setting up a new working copy.
We'll be able implement this feature quite easily using the WC-NG datastore. It will take just a few operations:
- preserve all metadata about local changes
- place a copy of each locally-modified into pristine storage, recording their SHA-1 key with the stashed metadata
- revert all local changes
Recovering the changes from the stash is effectively running a big "svn merge" operation. The merge is required because you may have made other changes to the working copy (your bug-fix) and/or updated to the latest revision.
Other features, such as multiple stashes, management of those changes, applying subsets, and whatnot would be added, too. The feature set has not (yet) been designed, so I have no idea what is required or how we would present this to our users. We'll definitely be looking at git and hg as we explore the needs around stashing/shelving.
"When?" is your next question, I'm sure :-) ... Well, we're releasing WC-NG in Subversion 1.7. That will probably happen this fall. We want to get those changes out the door since that will mark 18 months of development time. WC-NG is a feature in itself, and we want to get it into people's hands without further delays [waiting for additional features]. After that, I'm interested in adding stash support (and a "checkpoint" feature (described in my next post)). So let's say stashing will appear in 1.8 which should be released around this time next year.